The New Zealand Mud Snail (Potamopygrus antipodarum) is an exceptionally hardy invasive species that colonizes damaged streams and competes with native species like mayflies, caddisflies, and trout. The snails can pass through the digestive tracts of fish unharmed, and can live out of water for nearly a month in damp or shady environments. Because the snails can reproduce without fertilization, it only takes one individual snail to create a colony that can heavily impact a stream.

While the snails had been found in the Upper Owens River in 1999, until recently they had not spread to the Mono Basin. However, in the spring of 2005, a California Department of Fish and Game survey team reportedly found New Zealand Mud Snails in Rush Creek upstream from Highway 395.

On September 8, 2006, Dr. David Herbst of the Sierra Nevada Aquatic Research Lab was unable to find the snails in the same Rush Creek location--he only found native snails. Based on his survey effort and the type of habitat and water quality that the NZMS prefer in the Upper Owens River, he thinks it is unlikely that the snails are in Rush Creek!

The snails spread to new streams mainly by hitchhiking on humans, so it is important to be vigilant about cleaning gear that has been in a snail-inhabited stream like the Upper Owens River. Cleaning boats with hot water and bleach effectively removes snails from surfaces (but does not kill them!), while boots, shoes, waders, and equipment should be frozen overnight to eliminate the chance of contaminating other waters. When you visit the Upper Owens River, or any other stream in the Eastern Sierra, please do your part to stop the spread of New Zealand Mud Snails!